1. Field of the Invention
The present invention relates to a control system for a materials-handling device, especially for a shelf storage and retrieval device, including a horizontal travelling mechanism having a horizontal drive (x); a lift truck, which can be raised and lowered on a mast via a lifting drive (y); and a storage/retrieval drive (z) for storage or retrieval of the material to be handled.
2. Description of the Prior Art
Rail-mounted materials-handling devices for the transport, storage and retrieval of unit loads, e.g., pallets in shelf warehouses, are well known. The transport and warehousing operations of the storage and retrieval device are carried out along a passageway, the longitudinal sides of which each form a shelf. The storage and retrieval device is equipped with a travelling drive in the x-direction and a lifting drive in the y-direction for transporting the unit load along the shelf. The storage and retrieval of the unit load on and from the shelf is carried out by a driven telescopic or drawing device which works in the z-direction and is positioned on the lifting device moved by the lifting drive.
The travelling drive moves the device on the travelling rail along the length of the shelf. The lift truck is run on a mast of shelf height, and is raised or lowered using a support device, e.g., cable or chain.
A control job for the automatic sequence of transport and storage operations includes essentially position control for the travelling and lifting devices and position and process control during the storage and retrieval process carried out by the load holding device on the lifting device.
The drives and associated sensors for the movement sequences are concentrated locally on the travelling unit and the lifting device. The necessary electrical signal connections and the motor feed line are run via the mast, which is otherwise needed only for mechanical support and guidance functions. According to the prior art, these electrical connections are established by cable lines between the travelling unit and the lifting device. Trailing cable connections of this type can have up to 140 leads and require high installation expenditure. In addition, such a structure entails great expense for cabling to the height-adjustable lifting device. In cable connections between the lifting device and the mast, on the one hand, and between the mast and the travelling unit, on the other, the establishment of control can be terminated only in connection with the mast. Given the size of the storage and retrieval device, it is important, for reasons related to manufacturing technology and transportation between the manufacturing site and the usage site, to be able to manufacture the lifting device, mast and travelling unit separately and to establish the electric connections at the interfaces of these modules upon assembly. In addition, expenditures for cable lines as used in prior art devices and for their required assembly as well as for the maintenance necessitated by ongoing bending stress are extremely high.